Preparing a corrective lens for eyeglasses comprises firstly a step of optically designing and shaping the refractive faces of the lens, and secondly a step of adapting the lens so that it fits the selected frame.
The present invention relates to measuring geometrico-physionomic parameters on the wearer's face that enable account to be taken of the configuration in which the eyeglasses are positioned on the wearer's face. These parameters are likely to be used in both of the steps of preparing a corrective lens so as to ensure that the lens ends up performing the corrective optical function for which it is designed and prescribed. These parameters include, for example, the heights of the centers of rotation of the eyes and the pantoscopic angle of inclination formed by the general plane of the frame or the à relative to the vertical.
In order for these parameters to be taken into account effectively, they need to be measured with care and accuracy, and that is found to be difficult in practice. To rationalize the taking of measurements, proposals have made for measurements to be taken from digital photographs of the wearer's face wearing the frame. Thus, by way of example, the pupillary distance and the pupil height can be measured by processing a digital front-view image of the wearer's face.
One known image capture appliance is mounted so as to be movable vertically on a stand column that ensures that the optical axis of the lens of the image capture appliance remains horizontal and can be adjusted to have the same altitude as the wearer's eyes so as to enable accurate measurement to be obtained of the geometrico-physionomic parameters of the wearer.
Nevertheless, the resulting measurement-taking device is found to be relatively bulky and not very ergonomic for use on sales' premises. The measurement-taking protocol is perceived as being relatively constricting, lengthy, and fiddly both by the wearer and by the optician. That device is also very expensive.